CVE-2007-3724 in Windows
Summary
by MITRE
The process scheduler in the Microsoft Windows XP kernel does not make use of the process statistics kept by the kernel, performs scheduling based on CPU billing gathered from periodic process sampling ticks, and gives preference to "interactive" processes that perform voluntary sleeps, which allows local users to cause a denial of service (CPU consumption), as described in "Secretly Monopolizing the CPU Without Superuser Privileges."
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Analysis
by VulDB Data Team • 04/07/2017
The vulnerability described in CVE-2007-3724 represents a fundamental design flaw in the Windows XP kernel's process scheduling algorithm that creates a significant denial of service risk. This issue stems from the kernel's failure to properly utilize the comprehensive process statistics that are maintained internally, instead relying on an outdated and inefficient method of CPU allocation based on periodic sampling ticks. The scheduler's reliance on voluntary sleep patterns to determine process priority creates a exploitable condition where malicious processes can manipulate their scheduling behavior to maintain excessive CPU usage over extended periods.
The technical implementation of this vulnerability exploits the kernel's specific handling of interactive process detection and CPU billing mechanisms. When processes voluntarily sleep, the scheduler incorrectly interprets this as evidence of interactive behavior and grants them preferential treatment in CPU allocation. This design choice, while intended to improve user experience by prioritizing responsive applications, creates a predictable attack vector where local users can craft processes that repeatedly sleep and wake to maintain elevated scheduling priority. The vulnerability specifically targets the Windows XP kernel's scheduler implementation and is classified under CWE-200 as an improper access of system resources.
From an operational impact perspective, this vulnerability enables local users to consume excessive CPU resources without requiring administrative privileges, effectively creating a denial of service condition that can severely degrade system performance or render the system unresponsive. The attack mechanism is particularly insidious because it operates entirely within the bounds of normal user privileges, making detection and prevention challenging. The vulnerability allows attackers to maintain sustained CPU monopolization that can persist for extended periods, potentially causing system instability, application crashes, or complete system hangs. This condition directly violates the principle of least privilege and demonstrates a critical flaw in resource management within the Windows XP kernel architecture.
Mitigation strategies for this vulnerability should focus on both immediate system hardening and long-term architectural improvements. System administrators should implement process monitoring and resource limiting mechanisms to detect abnormal CPU usage patterns, while also considering kernel updates and patches that address the scheduling algorithm deficiencies. The vulnerability highlights the importance of proper resource accounting in operating system kernels and aligns with ATT&CK technique T1496 for resource exhaustion attacks. Organizations should also implement process isolation and privilege separation measures to limit the potential impact of such exploits, while maintaining compliance with security frameworks that emphasize proper access control and resource management. The vulnerability serves as a critical reminder of the importance of robust kernel design and the need for comprehensive testing of scheduling algorithms under various threat scenarios.